During the Gulf War many casualties were caused by fratricide, i.e. friendly troops shooting at and killing each other. The ability of recognizing friend from foe in a fast changing electronic warfare environment is therefore of the utmost importance. A method for identifying friend from foe is disclosed in a recently filed patent application entitled "Phosphorescent Light Panels--A Solution To The Fratricide Problem", by two of the co-inventors of the instant application.
To reduce casualties due to friendly fire, a positive identification may be provided by mounting a beacon to a vehicle.
A solution offered by the Night Vision and Electrical Optics Laboratory (NVEOL) of the Department of Army uses a thermal identification device. The device can be activated either remotely by a laser or from within the vehicle when positive identification is required. The thermal identification device consists of two plates joined together in an inverted-V shape on a roof. One of the plates is heated by a current passing through wires on the surface of the plate. The other plate is made of aluminum and reflects the temperature of the sky. The temperature difference between the two surfaces of the plates is a function of range, as the aluminum plate surface is susceptible to variations in the daily weather conditions, such as the time of day, the ambient temperature and cloud cover, etc. The thermal identification device is positioned on top of an aluminum tube having coupled thereto a motor and a slip ring, through which an appropriate voltage is applied to turn the motor.
Sometime in October 1992, there was issued by the National Training Center a requirement of a kill indicator for a vehicle (such as an M1 tank) to allow an attack helicopter to see that a tank has been struck by laser bullets. The present indicator on the M1 tank in use at the National Training Center is inadequate insofar as it consists of a Whoopee light that spins around on top of the tank when the tank's Multiple Integrated Laser Engagement System (MILES) registers a hit. This light is not visible to a helicopter pilot using a forward looking infra-red sensor (FLIR), i.e. the requirement further mandated that the kill indicator should function as a beacon and be visible under all weather conditions.
At first, the use of the thermal identification device as a solution to the problem became apparent. In other words, the thermal identification device can be connected with the Whoopee light so that when a MILES hit is scored, both the Whoopee light and the thermal identification device are activated. The temperature difference between the heated plate and the sky-reflecting plate would be observed by the helicopter's FLIR. The larger the temperature difference the further the visible distance. Unfortunately, the thermal identification device cannot beacon if the weather is cloudy, rainy or foggy.
There is therefore a need for a thermal identification device that is operational and visible under all weather conditions.